Therapeutic effectiveness of an intravenous immunoglobulin with pH 4.25 in experimental neonatal sepsis caused by Klebsiella pneumoniae

: The in vitro opsonic activity and in vivo therapeutic effect of an intravenous immunoglobulin (IGIV) pH 4.25 against Klebsiella pneumoniae were evaluated in this study. By an opsonophagocytic assay in microtiter plates, bacteria were opsonized with IGIV pH 4.25, 10% rabbit serum, or 10% rabbit serum heated at 56 degrees C for 30 minutes. Opsonized bacteria were challenged with polymorphonuclear leukocytes (PMNs) from normal adults and bacterial killing was measured at 60 and 150 minutes. Forty-four newborn Wistar rats were infected subcutaneously with a 75% lethal dose of Klebsiella pneumoniae, and 90 minutes after, 24 rats were assigned to receive 500 mg/kg of IGIV pH 4.25 by intraperitoneal route and the remaining 20 animals received an equal volume injection of PBS. Animal survival was observed during a ten-day period. The best bacterial killing index was reached when bacteria were previously opsonized with IGIV pH 4.25 at 60 minutes (p less than 0.001), as well as at 150 minutes (p less than 0.0001) of challenge with PMNs. Newborn rat survival was better in the IGIV group (17/24), than PBS group (5/20), with significant statistical difference (p = 0.0029). These data suggest IGIV pH 4.25 can be a useful adjunct in the treatment of Klebsiella pneumoniae newborn sepsis.